Time for action – drawing Lissajous curves

The Lissajous figures are determined by four parameters A, B, a, and b. Let's set A and B to 1 for simplicity:

1. Initialize t with the linspace function from -pi to pi with 201 points:

   a = float(sys.argv[1])
   b = float(sys.argv[2])
   t = np.linspace(-np.pi, np.pi, 201)

2. Calculate x with the sin function and np.pi:

   x = np.sin(a * t + np.pi/2)

3. Calculate y with the sin function:

   y = np.sin(b * t)

4. Matplotlib will be covered later in Chapter 9, Plotting with Matplotlib. Plot as shown here:

   

   plot(x, y)
   show()

   The result for a = 9 and b = 8:

What just happened?

We plotted the Lissajous curve with the previously mentioned parametric equations where A=B=1, a=9, and, b=8. We used the sin and linspace functions as well as the NumPy pi constant (see lissajous.py):

import numpy as np
from matplotlib.pyplot import plot
from matplotlib.pyplot import show
import sys

a = float(sys.argv[1])
b = float(sys.argv[2])
t = np.linspace(-np.pi, np.pi, 201)
x = np.sin(a * t + np.pi/2)...